Broken Exhaust Manifold Bolt - Page 3 - Chevy Impala SS Forum
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post #21 of 27 (permalink) Old 01-23-2017, 07:21 AM Thread Starter
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I Hereby Degree -

- as the OP I ordain no hatin' on my thread. FTR, there's no end to applications for a good glop of RTV:



You just have to weigh effort to benefit. In this case I had used the same hack with success for many years on an earlier car. And, it got the car back on the road way sooner than welding or replacing = = which I'll eventually do.

In the case of ex. manifolds I admit I took the extra time on my approach since a perfect seal impacts so many aspects of engine operation.

\'96SS SOB: SSRI, Herter Tune, Tri-Y II, SLP SS, 3000 Edge, F/HO bars, METCO extendeds and CV MMC, Bilsteins, currently Vredestein Ultrac Sessanta (315/35 rear)
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post #22 of 27 (permalink) Old 01-28-2017, 11:40 PM
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Certainly not needed, and specifically contra-indicated. Headers are constructed of steel tube, way more flexible/malleable and less crack-prone than cast metal.
This actually got me thinking and I haven't had a chance to get back to it until now. On these cars the exhaust has no flexibility whatsoever built into it. On the original setup it's bolted solidly to the motor, bolted solidly to the cats and then bolts solidly underneath the car. The motor however is free to move a bit in its mounts, especially when they age and wear out. I've noticed that with mine when I give it a good rev, the motor torques a fair amount to one side, as any motor normally would. Could that stress on the exhaust have anything to do with bolts coming loose and/or breaking off? And should I be concerned with my new system since I did find a way to attach it to the original mounts underneath the car?

I have a few thoughts on it, and maybe there's nothing to worry about, but figured it was worth asking. I could disconnect the mounts that I added and allow the exhaust to be supported by the muffler hangers so that it has some movement when the motor twists under heavy throttle, probably wouldn't hurt anything especially given the weight reduction by eliminating the cast iron manifolds and deleting the cats. I just assumed with those long sections that keeping them contained may reduce or prevent unwanted rattles and other such noises. Also since the cats are gone, it'd be the perfect spot to graft in a couple flex pipes, although I'd been considering grafting in some dumps there for no reason other than to make ricers who run fart cans wet themselves if they pull up next to me at a light.

Obviously I can probably mitigate some of the issue by putting in new motor mounts, but I have no current plans for that since, well, I have motor mounts that currently contain the motor more or less in the engine compartment and I'd rather focus on other projects for the time-being. Let me know what your thoughts are or if I'm just being paranoid and silly.

Something witty.
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post #23 of 27 (permalink) Old 01-29-2017, 03:35 AM Thread Starter
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You're not paranoid and silly, just have way much not enough other things to keep you busy. And the exhaust does have flexibility as the manifold heats up and slips around inside the oversize bolt holes. As I said be sure to use all those cast iron spacers per original placement, and don't over-tighten the bolts. And replace everything with GR8. Also, IDK about today but flex pipes on the exhaust was good for fail during inspection. You don't want it under a car for obvious safety reasons.

\'96SS SOB: SSRI, Herter Tune, Tri-Y II, SLP SS, 3000 Edge, F/HO bars, METCO extendeds and CV MMC, Bilsteins, currently Vredestein Ultrac Sessanta (315/35 rear)
\'96FWB BUW-Butt Ugly White: SS Bars, METCO LCAs, Koni Reds, PowerTrax No-Slip
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post #24 of 27 (permalink) Old 01-29-2017, 03:56 AM
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You're not paranoid and silly, just have way much not enough other things to keep you busy. And the exhaust does have flexibility as the manifold heats up and slips around inside the oversize bolt holes. As I said be sure to use all those cast iron spacers per original placement, and don't over-tighten the bolts. And replace everything with GR8. Also, IDK about today but flex pipes on the exhaust was good for fail during inspection. You don't want it under a car for obvious safety reasons.
I thought the cast iron spacers were not recommended when using headers, it has been a little while though, I may need to go back and re-read some of the posts and double check that. I believe the bolts that came with my headers are stainless steel, so they'll be of similar strength to grade 8 hardware. And it occurred to me there's more than one type of flex pipe, so to clarify what I was thinking of I'll attach a pic. Obviously something of decent quality, not cheap ebay junk. And not sure about inspection, if you're referring to emissions we won't ever have that here. If you're referring to race tracks or drag strips, while I don't plan to do any of that with the car, I might want to run it down a drag strip on occasion just to see what it can do.

And yeah, winter is starting to get to me so I'm going a little stir crazy. I have a few things to do once it warms back up, but I'm starting to get impatient for spring. Spending my free time sitting around annoys me, I'd rather be outside wrenching on something.
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post #25 of 27 (permalink) Old 01-29-2017, 04:20 AM Thread Starter
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You're right - nix the spacers with headers of course. I was referencing the "flexibility" even in the stock configuration.

And I was in fact referring to the old chintzy flex pipes from JC Whitney. Even before there was an emissions test, old style flex pipes would fail the safety inspection. They erode and rust and crack and leak.

Nice exhaust install thread you did.

\'96SS SOB: SSRI, Herter Tune, Tri-Y II, SLP SS, 3000 Edge, F/HO bars, METCO extendeds and CV MMC, Bilsteins, currently Vredestein Ultrac Sessanta (315/35 rear)
\'96FWB BUW-Butt Ugly White: SS Bars, METCO LCAs, Koni Reds, PowerTrax No-Slip
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post #26 of 27 (permalink) Old 01-29-2017, 04:40 AM
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You're right - nix the spacers with headers of course. I was referencing the "flexibility" even in the stock configuration.

And I was in fact referring to the old chintzy flex pipes from JC Whitney. Even before there was an emissions test, old style flex pipes would fail the safety inspection. They erode and rust and crack and leak.

Nice exhaust install thread you did.
Gotcha, that's what I thought, about the spacers that is. I'm still not sure about using a flex pipe, I've seen them on OEM setups before so that's where I got the idea. If they're decent quality they do seem to last a long time. Anyways, I definitely appreciate your input.

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post #27 of 27 (permalink) Old 01-29-2017, 03:34 PM
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Quote:
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The premise for those cast spacers is to allow lateral slip as the cast manifolds heat up and permit expansion without cracking from stress. I noticed as you that the protruding amount on mine was the same length as a spacer and realized the bolt snapped right at the head. Those spacers go on all bolts except the 2 centerboard locations each bank, though I've NEVER heard of cyl. 1 and 2 bolts breaking.

The only question I have is why spacers became a "thing" with this motor. I've seen maybe the same rough cast iron type regular washers on some motors, but certainly not the tall ones as on an LT-. I don't recall them on prior SBC and other old cars. Perhaps cheaper more crack-prone pot metal used in the manifolds? Or "improved" flow with increased lever arm thermo somethings in the oem design causing way more stress? All I know is be sure to use all those cast iron spacers per original placement, and don't over-tighten the bolts. It should have been a TSB way back when.


EDIT: Pic of said layout for ref

The LO3/5 has fairly tall spacers as well, but not quite as tall the LT1 items.


I found a tool for drilling the bolts out. I took a picture of the ad in a magazine last week. Price is a little salty at $149.00 plus shipping.
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1991 OCC 461 (.030 over 454) BBC, 3.23 posi, flash to pass, drop spindles & springs, custom fender skirts, Impala rims, Recaros, Blazer console, MOMO/wood SW w/QR, custom wood shift knob, Pioneer DEH P77DH
1992 OCC now with 5.7 tbi, DEH P77DH
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Last edited by Fred Kiehl; 01-29-2017 at 05:12 PM. Reason: added price
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